Asphalt patching systems are well known in the art. For example, U.S. Pat. No. 5,263,790 issued Nov. 23, 1993 and U.S. Pat. No. 5,419,654 issued May 30, 1995, teach a patcher comprising a motor driven, wheeled vehicle having a gravel hopper and a storage tank for liquid asphalt, as well as pressurized conduits for respectively advancing gravel and asphalt to a mixing head. The asphalt emulsion is delivered from the storage tank to the mixing head by feed lines. The mixing head is arranged to extend from a free end of a swingably mounted, telescoping boom, which is moveable in both horizontal and vertical planes as well as being selectively extendable and retractable to expedite desired positioning of the mixing head above a roadway surface to be patched. The pressurized conduits may also be initially employed to blow debris from the pothole or crevice being patched whereupon asphalt, with or without aggregate, is delivered to the mixing head. The need for rolling or tamping is eliminated by the use of high-pressure air.
The feed lines carrying the asphalt emulsion must be cleaned on a regular basis, typically at least once per day.
Present day cleaning operations have the disadvantage of expelling a significant amount of asphalt emulsion and solvent during the cleaning process which constitutes an environmental hazard as far as safe disposal of the emulsion and solvent is concerned, as well as requiring means for collecting and storing the hazardous material and further requiring labor intensive activity in the performance of the cleaning operation. It is therefore desirable to provide method and apparatus for performing a cleaning operation which significantly reduces the labor intensive activity and, in one embodiment, substantially eliminates such labor intensive activity by performing the cleaning steps substantially automatically, as well as retaining the emulsion and solvent in the patcher and avoiding need for discharge of these materials during the cleaning operation and providing for continued reuse.